1. Field of the Invention
The present invention generally relates to an apparatus for flameout detection to be used with furnaces.
2. Description of the Prior Art
Flame detecting apparatuses are commonly used for monitoring burner flames as part of maintaining safe furnace operating conditions. For instance, if fuel is continuously fed to a burner even though the flame has failed to ignite or has become extinguished, an undesirable explosion may result. Thus, flame detecting apparatuses have been used to monitor burner flames and to trigger relays for sounding alarms and cutting off fuel supply in the event of flameouts.
Various types of flame detecting apparatuses have been disclosed in the prior art, with some types enclosed in furnaces and others disposed to the exterior of the furnaces. The internal flame detecting apparatuses are usually proximate to the flame, whereby, in addition to flameout detection, flame intensity can be measured to provide further combustion information. However, the replacement of furnace-enclosed apparatuses involves complicated and/or lengthy procedures which must be followed to prevent hazardous situations.
On the other hand, furnace-external flame detecting apparatuses, though often limited to flameout detection, are more easily accessed. For instance, U.S. Pat. No. 6,127,932, issued to Wilson et al. on Oct. 3, 2000 discloses a sensor disposed at an open end of a closed-end tube. The closed-end tube extends from the exterior of the furnace and reaches the flame. The sensor is concentrically disposed on a circular plate of greater diameter than the tube, whereby the sensor is sealed off from any external light when disposed in the tube so as to only respond to light emitted from the flame. An electrical connection extends from the free surface of the circular plate for connection to an electrical outlet.
U.S. Pat. No. 6,080,223, issued on Jun. 27, 2000 to Mavronis discloses a connection mechanism for securing a flame detecting apparatus to a sight hole of a furnace. The sight hole of the furnace is surrounded by a flange, and resilient arms extend forwardly from the apparatus to exert pressure on the flange, whereby it is secured thereto. Once more, the sensor portion is isolated from any external light. It is noted that an electrical wire extends from a free end of the sensor for connection to an electrical outlet.
Flame detecting apparatuses are exposed to a harsh environment and may need frequent replacing as they are in contact with high temperature surfaces and electromagnetic impulses. One of the advantages of the existing furnace-external flame detecting apparatuses resides in the fact that they are more easily accessed and replaced than internal models. However, the replacement involves disconnecting the apparatuses which may also involve cutting wires. In some instances, it is even required to turn off the furnace to attend the electrical connections.
Also, furnace-external flame detecting apparatuses have been used with furnaces having a pivotable sight hole tube. These sight hole tubes are pivotable such as to be longitudinally aligned with the flame to be inspected, to ensure the flame is visible therethrough. Furthermore, the practice of visually inspecting the flame is common as it may indicate burner problems not detectable by the flame detecting apparatuses. For example, the color of the flame may indicate inefficient combustion. The above described prior art devices do not allow the visual inspection of the flame as they completely seal the sight hole of the furnace to avoid being exposed to external light.
It is therefore an aim of the present invention to provide an apparatus for flameout detection external to a furnace also allowing flame visibility for alignment of the apparatus and visual inspection.
It is also an aim of the present invention to provide an apparatus for furnace flameout detection having a sensor element detachable from a fixed portion for facilitating the replacement thereof.
It is a still further aim of the present invention to provide a method for replacing a furnace flameout detecting apparatus overcoming the above mentioned disadvantages of the prior art.
Therefore, in accordance with the present invention, there is provided an apparatus for flameout detection to be used with a furnace having a sight hole tube for flame inspection. The apparatus comprises a body adapted for being mounted to the tube. The body has a sensor device being positioned opposite a sight hole of the sight hole tube for flameout detection and has a see-through portion for flame visibility through the apparatus.
Also, still in accordance with the present invention, there is provided an apparatus for flameout detection to be used with a furnace having a sight hole tube for inspection of a flame. The apparatus comprises a fixed portion adapted for being mounted to the sight hole tube and being electrically connected to a control system. The fixed portion defines a first see-through portion being positioned opposite a sight hole of the sight hole tube, whereby the flame is visible therethrough. A detachable portion has a sensor device therein and is releasably mounted to the fixed portion such as to engage a contact connection therewith. The sensor device is disposed opposite the first see-through portion of the fixed portion for flameout detection therethrough, wherein the detachable portion is electrically disconnected upon being detached from the fixed portion.
Further in accordance with the present invention, there is provided a method for installing a flameout detection apparatus to a sight hole tube of a furnace and replacing the flameout detection apparatus. The method comprises the steps of (i) securing a fixed portion of the flameout detection apparatus to the sight hole tube of the furnace, (ii) wiring the fixed portion of the flameout detection apparatus to a control system, (iii) electrically connecting a detachable sensor portion of the flameout detection apparatus by securing same to the fixed portion, (iv) when the detachable sensor portion requires to be replaced, disconnecting the detachable sensor portion by detaching same from the fixed portion, and (v) repeating step (iii) with one of the detachable sensor portion having been repaired and another detachable sensor portion.